Remember, West Bend 820s are industrial engines used on tampers, pumps and even drones, designed to run at lower constant RPMs. The technology dates back to the 1960s. They are not the more sophisticated engines that you mentioned.

One constant is that 820s need to run very fat, to the plug fouling fat on air/fuel ratios,

Opinions, even from the Yamaha and Rotax owners, differ greatly on the oil and octane to be used..c_________________"kart racing since 1958, was and still the best bank for the buck in motorsports"

JW-you did mention using higher octane gas for the Yamahas and Rotaxs. I was running 87 octane. I did over rev one of the two engines last year at Barnesville when I lost a chain on one engine. And with all 4 engines, I was running them too lean.

I blew one of two engines on the dual at little Talledega GP track, which is a larger track. I put a rod through the case on one, ran the other ran as a single many laps with no problem.

Engines may have been geared too low for duals, over reving them. Also it is hard to monitor both engines running together. I plan to monitor rpms and temps better with TWO gauges. c_________________"kart racing since 1958, was and still the best bank for the buck in motorsports"

Read this and it will explain all about fuel. Your engine fuel mixture actually says 24-1 with 87 octane. Since you are operating it on a kart 93 octane will be plenty. Acetone is used in methanol for aid in cold starting and helps keep the oil in suspension and also help with water dispersal that accumulates in methanol. AV gas is designed for higher altitudes and has a lower Reid Vapor Pressurer than regular gas. Race gas is designed for race engines and high compression engines which you do not have. If you decide that you must have race gas I would cut 110 with regular 87 50% each which would give you 98., still not needed but would go farther and is cheaper than 98 race gas. 5% toulene added to 93 would be similiar to octane booster you buy at auto parts store and you can control it better with tolulene. Hp in a can is a slippery slope. Still think 93 & 8 oz. should be the ticket for your engines. Oil usually only drops the octane at most 2 points. Higher octane when not needed will actually hurt performance.